In Japanese Patent Application Laid-Open No. H05-257613, there is disclosed a hard-disc drive apparatus (hereinafter referred to as a “conventional apparatus”) which comprises a plurality of read/write heads arranged such that the hard disc is divided equally in order to shorten the read/write time of the hard disc and also to shorten the time required for reading/writing a plurality of tasks and/or the random access time to each track.
More specifically, this conventional apparatus comprises a control mechanism, a main buffer for reading/writing, two read/write heads A and B and sub-buffers each provided for a respective one of the heads. In the following, description will be made of an exemplary sequence for changing the operations of both heads in the conventional apparatus for the case where the operating condition in which the head A is writing into the disc with the head B reading from the disc is to be change, in response to a changeover request from the outside, to another condition in which the head A is in the read mode with the head B being in the write mode.
1. The control mechanism transmits to the head A a command for stopping writing.
2. Upon receiving the write stop command, the head A returns an acknowledgement of receipt of the stop command to the control mechanism.
3. The control mechanism waits for the acknowledgement of receipt from the head A. If the acknowledgement of receipt of the write stop command is not received, the control mechanism retransmits the write stop command to the head A. If the acknowledgement of receipt of the write stop command is not received from the head A in spite of retransmitting the write stop command a predetermined number of times, the control mechanism carries out an error processing.4. The control mechanism calculates the number of data transmitted to the write sub-buffer of the head A so far and, when the number has reached the end of one record, stops the transmission of data from the main buffer.5. The head A continues the writing operation until the data it has written reaches the end of one record.6. Since it is prohibited to change the write mode to the read mode during the writing operation, if a head mode change command is transmitted from the control mechanism, that command will be rejected.7. When the data have been written up to the end, the head A stops the writing operation and transmits to the control mechanism those numbers of the track and the sector, where the head A wrote the data last, together with the start location of the data remained unprocessed in the write main buffer.8. The control mechanism echoes the received data back to the head A.9. The head A receives the acknowledgment of receipt of data from the control mechanism, cancels the condition of rejecting the change of mode if the (echoed) data is correct, and informs the control mechanism of the cancellation.10. If the echoed data contains an error, the head A again transmits to the control mechanism a command for retransmitting echo data. If the data thus retransmitted has not been corrected, this writing operation is treated as an error.11. When a signal indicating that the condition of rejecting the change of mode has been cancelled is received from the head A, the control mechanism transmits, to the head A, a mode change command from the write mode to the read mode.12. The head A returns to the control mechanism an acknowledgment of receipt of the mode change command.13. The control mechanism checks the returned command and, if it contains an error, retransmits the mode change command to the head A. If the command again returned still contains an error, the mode change command is processed as an error.14. The control mechanism transmits to the head B a command for stopping reading.15. Upon receiving the read stop command, the head B returns an acknowledgement of receipt of the stop command to the control mechanism.16. The control mechanism waits for the acknowledgement of receipt of the read stop command from the head B. If the acknowledgement of receipt of the read stop command is not received, the control mechanism retransmits the read stop command to the head B. If the acknowledgement of receipt of the read stop command is not received from the head B in spite of retransmitting the read stop command a predetermined number of times, the control mechanism carries out an error processing.17. The head B performs the read operation until the data it has read reaches to the end of one record while calculating the number of data read so far and checking the amount of data.18. After the read operation ends, transmission of new data from the read sub-buffer associated with the head B to the read main buffer is stopped.19. Since it is prohibited to change the read mode to the write mode during the read operation, if a head mode change command is transmitted from the control mechanism, that command will be rejected.20. When the data have been read up to the end of one record, the head B terminates the read operation and transmits to the control mechanism those numbers of the track and the sector, where the head B read the data last.21. The control mechanism echoes the received data back to the head B.22. The head B receives the acknowledgment of receipt of data from the control mechanism, cancels the condition of rejecting the change of mode if the (echoed) data is correct, and informs the control mechanism of the cancellation.23. If the echoed data contains an error, the head B again transmits to the control mechanism a command for retransmitting echo data. If the data thus retransmitted has not been corrected, this read operation is processed as an error.24. When a signal indicating that the condition of rejecting the change of mode has been cancelled is received from the head B, the control mechanism transmits to the head B a mode change command from the read mode to the write mode.25. The head B returns to the control mechanism an acknowledgment of receipt of the mode change command.26. The control mechanism checks the returned command and, if it contains an error, retransmits the mode change command to the head B. If the command again returned still contains an error, the mode change command is processed as an error.27. The control mechanism confirms the fact that the operation modes of the head A and B have been changed over.28. The control mechanism informs the head A of those numbers of the track and sector where reading should be performed.29. The head A copies the data thus read to the read main buffer.30. The reading operation is continued.31. The control mechanism informs the head B of those numbers of the track and sector where writing should be performed.32. The head B copies the specified data from the write main buffer to the write sub-buffer associated with the head B.33. The writing operation is continued.
In the conventional hard-disc drive apparatus in order to carry out reading and writing with the two (i.e., the read and write) heads, in addition to the above-mentioned sequential processing of the lower level, a further sequential processing of the higher level must always be carried out, in which further sequential processing the track and sector at which writing is currently performed and the track and sector at which reading is currently performed are recognized, the track and sector at which reading must be performed next and the track and sector at which writing must be performed next are searched from a FAT (File Allocation Table), and these four values are then compared to determine what type of operation each of the head A and B must perform. One example of the higher level sequential processing is the shortest-time processing.
The shortest-time processing will now be described with reference to FIG. 3. It is here assumed that the rotary magnetic disc is rotating clockwise. FIG. 3 shows the situation in which the head A is writing into the sixth record (first track, seventh sector) as indicated by hatching whereas the head B has finished reading of the third record (first track, fourth sector).
For the processing to be performed next, there will be the following possibilities a and b:
a. The head A is moved to the third track to read the fourth record at the fifth sector, and the head B is moved to the fourth track to perform writing into the seventh record at the eighth sector.
b. The head A is moved to the fourth track to perform writing into the seventh record at the eighth sector, and the head B is moved to the third track to read the fourth record at the fifth sector.
In order to achieve the shortest-time processing, a calculation must be carried out in advance to determine which of the above operations a and b will be finished within a shorter time period.
In addition, if the user requests a special feature (e.g., a fast slip replay) to be performed, further processing which cannot be dealt with by such a simple comparison-based operation as that for the above-mentioned shortest-time processing will be needed. In such processing, it will be necessary to constantly examine whether or not the fast replay has overtook the recording, and, if it has, a more complicate control must be performed to deal with the plurality of heads which have the functions of switching between reading and writing.
In sum, the conventional hard-disc drive apparatus has to perform the read and write operations in correspondence with each of a huge number of combinations which are different in accordance with the locations of records to be accessed for reading/writing, the positions of the head A and B, the modes of operation of the heads A and B, and the special features. To implement this, the convention hard-disc drive apparatus must be provided with such a complicated and expensive read/write change control mechanism for which a control program composed of a huge number of program steps as well as a dedicated IC of a high processing speed must be developed.
On the other hand, in an information processing system provided with an information recording apparatus which reads files on an external storage medium such as a CD-ROM and MO, when a file of the external storage medium in which a virus program lies concealed is activated with the information recording apparatus of the information processing system being in operation, the virus program is executed, with the result that the information processing system may be destroyed. Conventionally, in order to avoid such destruction, viruses are removed in advance by means of vaccine software designed to remove virus programs. However, since new viruses constantly appear there exists no perfect vaccine software which can remove every virus program. In addition, any vaccine software currently available needs to be updated to its newest version always.
In recent years, there have been and are arising serious problems that home pages of governmental offices and companies are illegally altered by hackers. Conventionally, intrusions of hackers into a home page have been prevented by the provision of a firewall. However, hackers somehow create new techniques which are not rejected by such firewall, intrude into the server system for the home page and alter the contents of the home page which are stored in its hard-disc drive apparatus. Therefore, even when a firewall is provided and it is reinforced, there is a certain limit in preventing illegal intrusions into the home page by such firewall. In other words, in the conventional system, once the firewall is breached the system administrator has no means to counteract the hacker any longer. This is because the storage device in the conventional server system has only one read/write head used, so that the hacker can alter the home page if she/he has managed to reach the head.